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Need help finding replacement lead-acid battery for Robomower


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#31
neuronwelder

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The valve portion is a dead give away indicating they are gel cells. Only gel cells have valves for the sole purpose of venting off excess gases ONLY during an over charge or over voltage situation. (Don't go over 3 volts of battery voltage during charging - gel cells can't take this for long or they will vent and deteriorate) Otherwise they are completely sealed off from the real world not requiring any pressure differentiai because they don't vent like the old lead acid batteries do. I wonder if you can go to a Sears store and get an acceptable replacement? They have Optima batteries that are sealed gel cell batteries.Hawker batteries are on Ebay as well, and they have a great reputation. Be careful around all these batteries. Although they are small. They pack twice the punch as a full car battery.

Edited by neuronwelder, 29 June 2007 - 11:47 PM.




#32
neuronwelder

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The valve portion is a dead give away indicating they are gel cells and the vent is not normally used. Only gel cells have valves for the sole purpose of venting off excess gases ONLY during an over charge or over voltage situation. (Don't go over 3 volts of battery voltage during charging - gel cells can't take this for long or they will vent and deteriorate) Otherwise they are completely sealed off from the real world not requiring any pressure differential because they don't vent like the old lead acid batteries do. I wonder if you can go to a Sears store and get an acceptable replacement? They have Optima batteries that are sealed gel cell batteries.Hawker batteries are on Ebay as well, and they have a great reputation. Be careful around all these batteries. Although they are small. They pack twice the punch as a full car battery.

-banana-

#33
cron

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garsh...in your searches did you find an overall good place for these special type batteries?

I need a Yuasa NP7-12

the local batteriesplus has it for $29.99. I'm guessing it's a generic replacement which is fine.
Batteries.com has one for $21.22 with $7 shipping. (I missed a 35% off coupon by a few days)

#34
garsh

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garsh...in your searches did you find an overall good place for these special type batteries?

Not really.

Battery Universe appears to sell that particular brand/model: link
They also include a list of equivalent make/models at the bottom of the page.
I'm not sure how the price compares. Yuasa (now called EnerSys IIRC) seems to be considered one of the best makes available.
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#35
cron

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Yuasa (now called EnerSys IIRC) seems to be considered one of the best makes available.

thanks...found it for $24.90 shipped http://www.pacificba...slaspecial.html

#36
kas

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After skimming the following article, I thought of Garsh's search for a decent battery for the mower. But, if this new technology pans out, folks won't have to worry about Robomower quiting on the back 40.

Reclusive green-tech startup whispers a eulogy for the battery
Build the Border Fence


Given a choice, voters in the majority of states have reaffirm The Defense of Marriage Act, each and every time. It was wrong for judges and politicians to enact legal policies that are typically not honored in the majority of states. To be clear to the 'No H8' crowd, many Americans will never except an 'Adam and Steve' union as equal to a traditional marriage. It ain't hatery, they are just living their values.

#37
kas

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To keep your Robomower and the kids company.

Posted Image

Zeno Could Be Next Robot Boy Wonder
Build the Border Fence


Given a choice, voters in the majority of states have reaffirm The Defense of Marriage Act, each and every time. It was wrong for judges and politicians to enact legal policies that are typically not honored in the majority of states. To be clear to the 'No H8' crowd, many Americans will never except an 'Adam and Steve' union as equal to a traditional marriage. It ain't hatery, they are just living their values.

#38
yetiwisdom

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Garsh; I've read this thread and am in the same predicament this season - need a new battery but don't much want to pay $200. It seemed like you tried a lot of different batteries - what was your conclusion as far as best battery for the value? Thanks so much, :D James

#39
garsh

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I've read this thread and am in the same predicament this season - need a new battery but don't much want to pay $200. It seemed like you tried a lot of different batteries - what was your conclusion as far as best battery for the value?

Unfortunately, I found myself in the same predicament again this season. I run the mower once a day for 2 hours, every day that it's not raining. And the bad news is, I've yet to find a set of batteries that lasts more than one season.

I first tried these non-deep-discharge batteries because of the great sale that was going on at the time. Big mistake. They were never able to last for an entire 2-hour cut, and after two months they were barely lasting for an hour.

Next, I got the Tysonic deep-discharge batteries. These did pretty well, and they were the least expensive deep-discharge batteries I could find. But since they still didn't last an entire 2 hours at the end of the season, I tried another brand the next year.

Next, I tried the BB deep-discharge battery. More expensive, but it appeared to have better discharge characteristics. In the end, they didn't last any longer than the Tysonic batteries, so I wouldn't recommend paying a premium for them.

This year, I just ordered the Tysonic batteries again. In fact, they were just delivered today. I'll charge them up tonight and run the mower with them tomorrow. We'll see if they can make it through a whole cutting season.

I think I'm going to reprogram the mower to cut for less than 2 hours. The batteries should last longer if you don't run them down as far in between chargings. Maybe I'll try 1.5 hours and see how that goes.

Good luck!
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#40
yetiwisdom

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Thanks, Garsh. Are these the Tysonics you ordered, and was this the cheapest you could find?
http://www.discountp...teries/TY-12-18

Currently my batteries are lasting about 1.5 hours but because of a problem with my battery pack a couple of years ago I have an extra case, so I might get the Tysonics and a Fast Charger, but $175 for the Fast Charger is again way too steep. Anyone know of an appropriate charger for the Robo battery with perhaps clips that could be clipped to the terminals of the case?

Ideally (for me at least), I'd be able to get 2 full mows each time it goes out but that $175 is a bitter pill...

This is my 4th year on a Robomower and battery life has been an issue - after both my first and second seasons I sent the battery back to Friendly Robotics for Warranty Replacement because they had both failed despite careful winter maintainance and moderate use. I suspect this may be an inherent problem with the battery or the mower.

I like the Robo in all other regards (and love standing on my deck drinking beer and watching it work), but the batteries are a pain and each year I time how long they last at the beginning of the season and they've never broken 2 hours.

Edited by yetiwisdom, 24 April 2008 - 03:23 PM.


#41
garsh

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Are these the Tysonics you ordered, and was this the cheapest you could find?
http://www.discountp...teries/TY-12-18

Yes, and yes.

Anyone know of an appropriate charger for the Robo battery with perhaps clips that could be clipped to the terminals of the case?

A good, 24 volt fast-charger is hard to find, at least at a good price. You could consider opening up the battery case, disconnecting the two batteries from each other, reconnect them in parellel, and then use a good automotive 12v charger to charge them. I've done that. It's more work, but much easier to find a cheap 12v fast charger.

I suspect this may be an inherent problem with the battery or the mower.

I'm coming to that conclusion too.

Once this thing finally dies, I think I'm going to break down and shell out the money to get a Lawnbott. They use Lithium batteries which should last a lot longer. Plus they weigh a lot less. But I'm going to try to keep my Robomower running for at least one more season.
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#42
yetiwisdom

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A good, 24 volt fast-charger is hard to find, at least at a good price.

Okay, I'm a little clueless here but I'd like to look around for just such a charger (and will happily post results here). What would I be looking for as far as a charger - 24-volts and "x" number of amps? Would something like this do the trick?:

http://www.hardwarea...om/invt/1151976

Thanks again for all of your help. At this rate we should have a replacement set for all the overpriced Robo consumables!

#43
kas

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A good, 24 volt fast-charger is hard to find, at least at a good price.

Okay, I'm a little clueless here but I'd like to look around for just such a charger (and will happily post results here). What would I be looking for as far as a charger - 24-volts and "x" number of amps? Would something like this do the trick?:

http://www.hardwarea...om/invt/1151976


I can't give an opinion on the quality; but what I read sound good. Recharging at a slow pace and over charge cut off would be something I would look for. At least a 2 year warranty, since that charger ain't cheap. Since many small vehicles in service by the miltary use a 24 VDC electric system, one might look into what charger(s) are used by the Defense Department.

Also pick up a good "gravity" battery tester. Repeat recharging will kill any battery over time. The tester will let you know when a cell goes bad. When it's necessary to add water to a battery, always use distill water. Finally, if you value your vision, wear those safety glasses.
Build the Border Fence


Given a choice, voters in the majority of states have reaffirm The Defense of Marriage Act, each and every time. It was wrong for judges and politicians to enact legal policies that are typically not honored in the majority of states. To be clear to the 'No H8' crowd, many Americans will never except an 'Adam and Steve' union as equal to a traditional marriage. It ain't hatery, they are just living their values.

#44
garsh

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Would something like this do the trick?:
http://www.hardwarea...om/invt/1151976

Yes, that looks good. An equivalent 12v charger can be had for less than half of that amount.

The tester will let you know when a cell goes bad. When it's necessary to add water to a battery, always use distill water.

A tester is unnecessary for this application.
The mower will let us know when the cell goes bad - it will stop running. ;)
And these are sealed batteries, so adding water is not an option.
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#45
Oznog

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Hello guys,

For this info it would be best to join Robomower@yahoogroups.com
Let me cover some things though.
The "capacity" listed on the case is for a slow, 20hr discharge. For a 20AH batt that's a 1 amp rate for 20 hours.
Robomower draws current at around 3-5 amps, and 7-9 when stuck on something and the wheels spin. I'm uncertain of the best rate for approximation, but for an ideal yard where it NEVER gets stuck, if you have a 20AH batt and want to find the 5 amp capacity you look for the (5/20=0.25) 0.25CA rate. For lower capacities you'd have to look at a higher CA number. If your mower keeps hitting "low batt" when its gets stuck on stuff, that's 7 amps and look at the 0.35CA rate.

But not all batts are created equal, even though they come in the same case. The spec sheet of one designed for deep cycling like this should have cycle life depicted, and you want one rated for 300 cycles at 100% Depth of Discharge. I've seen ones only rated for 175x. If it's not listed, assume it's like 175. I've been through a number of "bargain" packs that lost capacity in a VERY short period of time.

At this time the batt which seems to be a safe bet is the B&B EVP20-12. This should yield about 3-4 hrs of runtime and is rated for 300x 100% DoD's. But here's the thing- as one person here experienced, the vendor may advertise an EVP20-12, but in fact he's saying it's an EVP20-12 replacement- and it'll be a crap battery, the only similarity is the physical size! I just got off the phone with refurbusa.com who clarified that indeed the one they list under EVP20-12 under a suspiciously cheap price is another type entirely, one blatantly NOT equivalent and unsuitable for Robomowing. Only 17.2AH, 175x 100% DoD rating, and a pretty low 7 amp rate capacity. It's from a name-brand mfg, but it is a cheaper product designed for standby float use, unlike the EVP20-12 is for frequent deep cycling.

Digikey.com is the vendor I'd recommend for the B&B EVP20-12. Only this model, "B&B" is not a magic name. B&B makes other batts including standby/floats in this case and they will likely crap out just like anybody else's. Digikey will never play substitution games! Right now that's $123.90 + shipping for 2x batts to make up one Robomower pack. This is much cheaper than anywhere else online I've found for B&B EVP20-12, actually. Unfortunately, the price of lead has absolutely skyrocketed in the last 2 years and lead-acid batts cost like twice as much across the board (if it makes you feel better, remember gas is 3x more!).

No brick-and-mortar in-town business will be able to give a comparable price, even when factoring in shipping. Literally, it would not be unusual to see a shelf price nearly 2x this and it's extremely unlikely you're going to find anything but the standby/float types which will crap out real fast in Robomower duty. You will probably see much more than the Digikey price for a B&B EVP20-12 stuck on this cheap, unsuitable type on an in-town business, so basically I think it's a waste of time to even look.

#46
garsh

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At this time the batt which seems to be a safe bet is the B&B EVP20-12. This should yield about 3-4 hrs of runtime and is rated for 300x 100% DoD's.

I actually tried this battery (bought from digikey, in fact), and found that it didn't last any longer than the Tysonic batteries. I was quite disappointed, since it does seem to be the best battery based on the spec sheet.

Perhaps I'm just too hard on the batteries, but I was hoping they would last more than one season.
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#47
Oznog

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I actually tried this battery (bought from digikey, in fact), and found that it didn't last any longer than the Tysonic batteries. I was quite disappointed, since it does seem to be the best battery based on the spec sheet.

Perhaps I'm just too hard on the batteries, but I was hoping they would last more than one season.


Interesting. They SHOULD last much longer. Even if we're talking about running them all the way down, they'll last longer. Are you SURE you got the EVP20-12, not another type of B&B battery?

#48
garsh

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I spoke to them just now and there's no such price.

The post you quoted was made two years ago.
The price of lead has skyrocketed since then.
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#49
dsimono

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Hi Guys... I just googled and ended up here. Great stuff. I am in the same boat as others... probably cheaper though and not technical with batteries... I just chatted with Digi-key...14 week lead time? Also they did not recomend the BP20-12 as a replacement. They did not have an alrernative either.

#50
garsh

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Are you SURE you got the EVP20-12, not another type of B&B battery?

Yep, I just now double-checked.

Also they did not recomend the BP20-12 as a replacement.

That's a general purpose battery. In general, lead-acid batteries are not meant to be discharged very far. They don't last very long when used that way. Deep-cycle lead-acid batteries are better for these applications, but their lifetimes are also pretty limited when you're always running them down to empty.

The Tysonic batteries mentioned earlier aren't bad. You might want to get a pair of those for now, AND order the EVP20-12's in time for next season. That's assuming that my personal experience with the EVP20-12 was not typical, and that they really are a much better battery.
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#51
Mulox

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I have a RL800 that is probably going to be due for some batteries soon. I had a pair of RL500's that worked for 4 years on the orginal YUSA batteries, then went to some other brand and had similar (poor) results to many on here, so I sold both and got the RL800. Anyone ever heard of Datascope? I found a pair of these for $84 shipped here: http://www.powerstar...pe_battery.html

Edited by Mulox, 03 July 2008 - 07:34 PM.


#52
garsh

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I have a RL800 that is probably going to be due for some batteries soon. I had a pair of RL500's that worked for 4 years on the orginal YUSA batteries, then went to some other brand and had similar (poor) results to many on here, so I sold both and got the RL800. Anyone ever heard of Datascope? I found a pair of these for $84 shipped here: http://www.powerstar...pe_battery.html

Nice find! I hadn't heard of them before now. If you try them out, let us know how it goes.

So far, the new Tysonics are doing very well. I'm only running the mower for a maximum of 100 minutes/day - I replaced the motherboard with a newer version, and the new one is much more time-efficient than the original RL500 motherboard, so I don't need to run it quite as long.
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#53
Mulox

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Thanks garsh, will do. Although now it seems I have another problem to take care of first. The left wheel is moving much slower than the right and roby is moving in circles. Left whel is making a grinding noise and getting some kind of gear/drive error that I need to look into... <sigh>

#54
JimTheFrog

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Hi guys,

Has anyone looked into LiFePO4 (lithium iron phosphate) batteries? They're touted as replacements for lead acid and have many advantages (steady discharge rate, no problem with deep discharge, very long life, environmentally friendly, etc.) But they're rather expensive. For example this one (http://www.all-batte...ebattery-1.aspx) is $250, and you might need to wire two in parallel to double the 8Ah capacity to get close to the capacity of the lead acid batteries we use for our Robomowers. On the other hand, since it can run until it's exhausted, maybe real life performance of a single 8Ah LiFePO4 would come out about the same. And it should last for years, unlike lead acid batteries that poop out after a year or two. So in the long run it's cheaper.

Of course the big question is whether or not it will even work in a Robomower and charger. (External fast charger, in my case, since both my mowers have flaked out and won't charge a battery.) The specs seem to indicate that it might work, but I'm out of my depth here. I'd love to hear from someone with more understanding of the details. Might be worth experimenting with.

--Jim

#55
garsh

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Has anyone looked into LiFePO4 (lithium iron phosphate) batteries?

No, I had never heard of them. I'll try to do a little investigation when I have a little free time.

Thanks for posting about them here and making us aware of the possible option! :)
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#56
garsh

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It's mowing season again, and the Tysonics that I bought last year are barely lasting for an hour now.

I just ordered a pair of these: Tempest 12v 22ah deep cycle battery
I'm hoping that the extra energy content means that I won't drain them as much, resulting in a longer life. It better, because these puppies are expensive!
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#57
dewolfxy

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I completely sympathize with the fun of using the robomower and also some fun in spending time tinkering with batteries and such, but at this point would you say the robomower has been a bit more of a time/money sink than it's worth compared to mowing the lawn yourself or paying someone? Seems like the batteries you've bought have run you into the several hundred dollar range in costs, and the robomowers are about $1-$2K depending on the model. Not a criticism, since I surely sink more "wasted" time into tinkering with things than I should, just curious what your assessment of the robomower is now that you can look back on having used it for a while.
Whatever is not nailed down is mine. What I can pry loose is not nailed down. - Collis P. Huntingdon

#58
garsh

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It's a fair point. The original batteries lasted two seasons, after having been sitting in a warehouse for who knows how long before that. So I have myself convinced that a decent battery should be able to last longer than one year. I'm just having a hard time proving it. ;) My allergies are bad enough that I would much rather spend this money than cut the grass myself. A lawn tractor (which I looked into purchasing before the woot robomower deal) would be much faster, potentially limiting my allergy issues, but costs more than the robomower and has more time-consuming maintenance issues. I haven't really looked into the cost of a professional grass-cutting service lately, but I believe it was more than paying for a new set of batteries. Plus everybody in the neighborhood knows me as the "guy with that mower". :)
"I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone." - Bjarne Stroustrup

#59
NARC

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I haven't really looked into the cost of a professional grass-cutting service lately, but I believe it was more than paying for a new set of batteries.

I would wager that it is - I pay $30/mow for college guys and that is on the low end of what it costs around here.

#60
dejavu

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