Replacing a lithium with a SLA battery - Updated with pics

[markwhalebone]

Hi there,

This is my first post here. I have searched the web and these forums for the answer to this question with no luck.

I have just bought my first electric bike and it came with a 36v 10.5ah lithium battery which needs replacing and I am wondering if I can replace this with a 36V SLA battery as I want to reduce my initial outlay since I do not know if I will stick with the bike.

Will an SLA battery work with motor controller and other parts of the e-bike or are these specific to the battery technology?

What about the charger - can I use the same one designed for 36v lithium to charge 36v SLA?

Thanks, Mark

 

[dogman dan]

Your bike will run fine on the same voltage of any kind of battery.

To use sla, you'd have to get an sla charger, but initially, you could get away with using the lithium charger for a short time. Sla chargers are cheap.

Unfortunately, the largest practical size sla is 12 ah, and you will fine good ones that work well with an EV are surprisingly expensive. I bet you are pricing the wrong kind of sla battery.

36v 12 ah lead, is good for about 5 miles max range. Yes, it will go farther, but with lead if you discharge more than 50% of it's capacity, you kill them. Like in 30 days. So if you ride 2-3 miles there and back, or charge every 5 miles, lead can work good. Heavy suckers, but still works for a short ride.

Hopefully you have a short ride. Are you young? At 25, I thought nothing of pedaling 10 miles.

 

[wesnewell]

Voltage is voltage. But you'll need twice the AH with SLA than with Lithium to get the same range, which will be many times larger and many times heavier.. There are all kinds of chargers, so without knowing the specs of yours there's no way to tell. But one can pick up a cheap 36V sla charger for $10 on ebay. What's wrong with your lithium pack? There's lots better options than going to sla without braking the bank. 6 of these would get you 10ah @44.4V nominal for ~$150. Range would be about 20 miles @20mph. You might need a new $20 charger. But the pack would only weigh ~7 lbs and be about the size of one of the sla batteries.
http://www.hobbyking.com/hobbyking/store/__18631__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack_USA_Warehouse_.html

 

[LSBW]

Here you go, these designed as drop-in lead acid replacements:

http://www.buya123batteries.com/ALM_12V7_p/400520-301.htm

Not cheap, but there will be minimum changes to your bike, and you can still use your SLA charger.

 

[markwhalebone]

Hi,
Thanks for the replies.

I didn't realise that I would need more Ah if I went with SLA - does this include the deep cycle ones such as

http://www.ebay.co.uk/itm/LUCAS-12V-7AH-SLA-Rechargeable-BATTERY-x-10-/190899793524?pt=UK_Health_Beauty_Mobility_Disability_Medical_ET&hash=item2c7283ae74

I am not sure what's wrong with the current battery, but the person I have bought it from says its lost power and will need a new one. Its a Sach Elo-2 and I found from the web it comes with a 10.5 Ah 36 V Li-ion battery as standard. I want to be able to ride at least 10-15 miles between charges.

Ok so I could look at combining smaller Li-ion batteries but I need to do a bit of reading as I hear playing around with Li-ion batteries can have some bad consequences! So if I had 6 batteries of 14.8V 5 Ah (connected as banks of 3 in parallel and then the 2 banks in series) I would, as you say have enough capacity. In this case I'm guessing charging wouldn't be that simple?

Thanks for the help. I will consider the suggestions.

 

[wesnewell]

Post a picture or link to your current battery pack. It's possible it just needs a little maintenance.

 

[dnmun]

Hi,
Thanks for the replies.

I didn't realise that I would need more Ah if I went with SLA - does this include the deep cycle ones such as

http://www.ebay.co.uk/itm/LUCAS-12V-7AH-SLA-Rechargeable-BATTERY-x-10-/190899793524?pt=UK_Health_Beauty_Mobility_Disability_Medical_ET&hash=item2c7283ae74

I am not sure what's wrong with the current battery, but the person I have bought it from says its lost power and will need a new one. Its a Sach Elo-2 and I found from the web it comes with a 10.5 Ah 36 V Li-ion battery as standard. I want to be able to ride at least 10-15 miles between charges.

Ok so I could look at combining smaller Li-ion batteries but I need to do a bit of reading as I hear playing around with Li-ion batteries can have some bad consequences! So if I had 6 batteries of 14.8V 5 Ah (connected as banks of 3 in parallel and then the 2 banks in series) I would, as you say have enough capacity. In this case I'm guessing charging wouldn't be that simple?

Thanks for the help. I will consider the suggestions.

why did the guy say it lost power? do you have the charger and did you try to charge the battery? do you have a voltmeter?

post up a picture of your battery with close up of the labels on the charger and on the battery.

 

[markwhalebone]

I am collecting the bike tomorrow. It comes with a charger and I will be able to do some investigation with a multimeter if needed.

What kind of maintenance can be performed on these types of batteries? Replacement cells maybe?

I will post a picture once I have the bike. For now this is all I have, it probably doesnt give much information;

 

[dogman dan]

Safe enough to assume you don't have the skills to revive that battery yet, even with help. But if you are lucky, it's just a matter of leaving it on the charger 24-7 for about a week. Or maybe fix a broken plug on the charger.

Get a voltmeter, the cheapest ones usually from Harbor Freight with an ad coupon. You are dead in the water without one. With a meter, we can help you figure out if it's just a charger you need.

But if you can afford it, a replacement lithium battery would be much better than lead. Unless, as I was saying, your ride will always be less than 5 miles.

I never recommend RC lico batteries to raw newbs. But with some time and reading here, you could learn to rig up RC batteries and use them safely, like many of us do. They can be very cheap, for 5 miles worth. And you can add more later for more range, as you can afford them.

 

[dnmun]

dogman is right. these lithium batteries last a long time so usually it is a bad connection or blown fuse in the charger or the BMS is turned off because of a loose sense wire that breaks out of the solder on the cell.

 

[markwhalebone]

Thank you very much. I will do some investigation once I get a look at the bike and battery, probably at the weekend. I am happy to open things up and have a look at connections. I have a (mechanical) engineering background but am completely new to batteries but am learning a lot.

I have been doing some reading around on these and other forums about building custom batteries from LiPo RC, 18650 and other lithium cells. I'm still getting my head around it as its quite complex with all the different chemistries and also how to manage the charging/discharging safely and other issues with BMSs.

I also have read in several places that reliable BMSs aren't yet available for these large lithium batteries - one thing that made me wonder is how come the e-bike suppliers can bundle a battery that is apparently safe to bulk charge (such as the one that came with the bike I am buying)? Have they developed their own BMS for this purpose or are they using a stock system that is apparently unsafe?

 

[friendly1uk]

I also have read in several places that reliable BMSs aren't yet available for these large lithium batteries - one thing that made me wonder is how come the e-bike suppliers can bundle a battery that is apparently safe to bulk charge (such as the one that came with the bike I am buying)? Have they developed their own BMS for this purpose or are they using a stock system that is apparently unsafe?

It is the same on all forums. There is always somebody dragging up outdated facts from the search engine and bringing them to new threads. You know what you have seen in real life. Even a car sized pack gets a bms. Everything does. We have lots of people here that try not to use one. Setting fires to light the way for anybody who's eye's are open. I'm glad you are questioning this obvious gap between what you read and the truth you see. Hopefully you won't be led astray by strangers.

You seem to have a charger and a bms already, along with some cells I guess need replacing. That seems the cheapest option to me. Just need to prove what the fault is before getting any money out. Individual cell voltages should be all you need for starters.

 

[Matt Gruber]

What about Bosch not using a bms? Might they actually employ engineers that know certain fuse protected LiMn204 cells are safe? Lots of "experts" on forums don't know how to build a safe battery without a bms. Bosch has real business experience, and a big, successful business. I'll trust them over a guy or girl that posts nonsense using a phoney name.
I tried to set a fire and the temp triggered fuse blew So how can a fire happen when the cell barely gets warm, and the fuse blows?
Not talking about cheap risky china cells. They are like smoking while gassing up a car.

 

[dogman dan]

Safe is a relative term. Sounds like you have the basic intelligence needed to make running an RC lico battery pack without a bms safe enough.

Best of both worlds, is to have a bms, but still have the ability to monitor the battery at the parallel cell group level easy. In other words, have a bms, but keep a wary eye on it. Confirm that it works initially, and then make sure it continues to function. Lots of people murder their bms, by smothering it in a bag on the bike. A bms needs at least some air cooling, or heat sinking. Some of this bms murder is done by the manufacturers. They know you are not mailing that thing back to china. Or they may have designed with other climates in mind. In other cases, they are just made with cheap components, and parts can fail at any time.

If you want to park and charge in a place where you would not build a campfire, then you do need to avoid cheap low quality manufactured RC batteries. Other types of battery is less likely to burst into flames. But the cheap RC stuff is well known to be low quality, and should never be trusted. You don't want to choose this kind, and live in apartments for example. Maybe, if your apartment has a fireplace. But most don't.

I've been running RC lico with no bms for four years now, with no fires. But I don't park and charge in the garage. Nor fall asleep while I'm charging the pack. Nor run or carry the pack carelessly. It takes vigilance, and a safe place to charge and store your pack to run lico "safe".

 

[friendly1uk]

What about Bosch not using a bms? Might they actually employ engineers that know certain fuse protected LiMn204 cells are safe? Lots of "experts" on forums don't know how to build a safe battery without a bms. Bosch has real business experience, and a big, successful business. I'll trust them over a guy or girl that posts nonsense using a phoney name.
I tried to set a fire and the temp triggered fuse blew So how can a fire happen when the cell barely gets warm, and the fuse blows?
Not talking about cheap risky china cells. They are like smoking while gassing up a car.

Hello Matt.
Nonsense? lol It's almost 100% sense. Your obscure example is very very unlikely. He will open it soon enough, then you will see what we are talking about.


Did you really use your proper name on an internet forum? I'm not sure if I should take you seriously or not. Did I at some point not indicate he should make his own mind up, making your 'expert' comments more a description of yourself than me?

Got a gratifying link to these bosch? I know they were spoke of here before.

 

[markwhalebone]

Ok here are some pics I took last night.

The battery has the plug for the bike (30A fused) and the charger - self explanatory. Then when I removed the battery from its case I found 2 additional connectors. The first has 22 terminals, grouped in pairs. The second has 4 wires coming to it (red, yellow, black, white).

Sorry these aren't great photos, I was pretty tired. I have the battery with me so I can take more if that helps. I can do some investigation with a voltmeter later on when I get home.

Here is the charger;

 

[markwhalebone]

A general photo to give an idea of scale

 

[dogman dan]

The many terminals plugs are for a bms. Either it was not used, or it was removed. I see no funky splices on the main discharge wires, so likely it was never used.

You can probe at those terminals with a DVM, and find out if any cells are dead, or just undercharged. You can use those same plugs to slowly charge one cell at a time too, with a single cell charger of some kind.

 

[dnmun]

i bet it is 10S limn2o4. there should be info somewhere. do you have a voltmeter?

 

[7circle]

The shape of side changes about 50mm from the top.
Suggests there is fair space after tops of the 10 pouches are terminated.
This chamber could contain the BMS and Circuits for charge and discharge FETs.
The 4pin connector could be serial port
or Shunt and Temp.
or Alarm Hvc Lvc
THe other connector looks like 11 holes
and 11 slots so the connector is keyed to only fit one way.

What is written on the Label near the bottom?

Take care not to shorts cells.
Sorry could be more helpful
Hope it is missing BMS not a faulty one in side.

 

[wesnewell]

Obviously a 10s battery pack. With the 10s balance plug, it looks like it was setup for an external bms or balancer that isn't there, or maybe it's just there for testing and never had one to begin with. Easy to test all cells on the balance plug. Check the individual cell voltages and see if one or more differs from the voltages of the others. If you get constant voltages across all the cells, just try and charge it using the 42V charger. If you find one or more cells too far off the voltage of most, then you'll need to balance them out before using the charger you have. In a well balanced pack all voltages should read within .05V of the others, but .1V would not be uncommon for a pack that hasn't been balanced for a while. And if its way under charged, say 3V average or less, they could be way out.

 

[markwhalebone]

Ok the 11 terminals seem to be the cell voltages as has been predicted. Not sure why there are pairs - they appear to be connected to the same things...

The differences between the 11 all measure between 4 and 4.2v except for one (between 2 and 3) which measures 0v. (Actually 25mV). I don't think its a bad connection because 2 and 3 are at the same voltage rather than either being disconnected.

So do I have a dead cell? Have the others been overcharged because of this? What now? I have a phone charger I could use to charge the dead cell perhaps, while monitoring the voltage...

 

[wesnewell]

Add all ten voltages up. Then compare it to the overall voltage of the pack measured at the discharge connector. If there's a 3-4V difference you have a loose balance wire to the cell. If it's about the same voltage, you've got a bad cell that needs replacing. Or bypassing until you can find a replacement cell. This is really simple stuff. Just 10 cells in series. Same principal as a multi cell flashlight.
You could try and salvage that one cell by doing a very slow charge on it until it reaches 4V, but you'd need to watch it closely. That's what I'd do, but 'm a cheap sob. A wag is that there was a bms on it that drew it's power from that cell. left sitting for a long period of time without use drain the cell.. That would have been a very slow discharge, so it might come back. I've never ran into the problem since I don't use a bms, but others have.

 

[torker]

Maybe the pair 2 and 3 is a ground ?? If you have 10 good cells you should get 42 volts fully charged. All good so far. Should be 41 or so now at the main discharge cable with a few cells lower. If so it should be enough to power the bike. Start looking at connectors.

 

[dnmun]

if you cannot determine that the 0V measurement is a measurement error or bad connection then you have to open the top of the shrink wtrap so you can expose the terminals of the electrodes.

do that and post up pictures.

also instead of just saying they are between 4 and 4.2 you should record the actual voltage to .01V and post up the list here.