SLA Battery Selection

[diverdon]

      Hello Everyone ,

           OK .. Another dumb question .. Maybe , I tried to use the search so as to not have to bug you all ..

      Been looking at the SLA batteries as I cannot afford a LiFePo4 right now .. My main decesions have been controlled by how much $$ each of the 4 batteries would be and the Amp Hour Rating Which is the Storage Capacity of the battery.. Right??

        Now just as I am about to buy the 4 batteries for 48 volts I am thinking about the (Output) rating . Or how many amps/watts each battery will deliver.. I have no Idea how to determine this ...Or how much I need ...Or if it is even a concern ..

      I do know enough to use heavy wire to do the wiring .. Like 10 guage maybe . And that I want 10 or 12 Amp Hour Capacity Batteries . Gotta take in the weight of the batteries also .

        But as far as telling how much "Output" there is I have no idea .. And haven't seen any talk about it in the several on line stores I've looked at


      As usual this is too long ... Sorry .. Thanks for all the help you've all given me .. Payday Friday .. Hope to have the bike goin on Monday ..

                                      Thanks Again , Don J. 

[diverdon]

      I'm trying to learn about this online .. No real luck .. I do know that the batteries at the local battery shop are Toyo 6 FM 10 models ... 12 volt 12 AH if that helps any .. But I can't find anywhere that tells the amp output or "C" rating as we call it in model airplane terms ... Thanks again , Don J.

[Gapy]

As I know, you should get enough current(power) out of it, but I am not exactly sure that it is good for battery! Usualy this kind of battery has a rank of 1C discarge-in your case this is 12 A, but if given a larger burden you can exceed this on 2C or 3C! Note that higher current cause suflation wich drastically reduce cycles! You should also know that if you discarge your SLA more than 75-80% you also reduce its life!

Gapy

[Balderdash]

I chose these 12V 7Ah SLA batteries for the best price/weight/performance ratio:

http://www.thebatteryshop.co.uk/np7-12l-yuasa-12v-7ah-lead-acid-battery-307-p.asp
http://www.yuasa-battery.co.uk/industrial/downloads/NP_pdf_downloads/NP7-12DataSheet-pdf.zip

A good charger is important too...I chose the Ctek one: http://www.ctekchargers.co.uk/ctek-xs800.php
The cheap one I had was overcharging and causing the cells to "gas".

I don't expect these batteries to last forever, but it was a cheap way to get started...

As for wiring I use mains solid core cable - the sort of stuff you use for a 30A ring main...it's what I had spare! (Not sure if it's 1.5mm, or 2.5mm squared)

[Leslie]

I use Ritar EV series.

http://www.ritarpower.com/products.aspx?catid=19&pcatid=

This is the model I use now and am glad to own them. Paid $100AUD each about $84USD.

http://www.ritarpower.com/upload/pdf/2009112110502551166858.pdf

24ah batts are 7.2kh each so you will need to mount them well.  reasoning behind the heavier models is that I do not usually discharge beyond 50% and these batteries are rated at 300 cycles at 100% dod.

So I should get a bit over a years usage if I ride the bike 10 rides per week at 50% dod.

It is worth getting lithium batteries IMO.

[Gapy]

Yes the charger is very important... I have CTEK XS7000 wich can also be used for reconditioning of any lead acid battery... DO NOT use an ordinary car charger-you can boil the cells! For SLA and VRLA is also better to charge with a higher voltage (14,7V) "snowflake mode" on CTEK.

[Leslie]

Yes the charger is very important... I have CTEK XS7000 wich can also be used for reconditioning of any lead acid battery... DO NOT use an ordinary car charger-you can boil the cells! For SLA and VRLA is also better to charge with a higher voltage (14,7V) "snowflake mode" on CTEK.

This 14.7v is good for fast charge and keeps sulphurnation levels low.

You can charge a battery to full with 13.7 volts but it may draw little current and take a long time.

In hot weather you should charge more slowly as the hot day can make electrolyte boil off too.

Here is some voltage/room temperature recommendations I posted a few weeks ago.



With many chargers you can not adjust so use a diode to lower voltage and remove or switch out in winter.

Even if it is in float at 13.6 overnight 12 hours this will finish charge.

I built a charger from a 27v 3 amp transformer, voltage doubler for 72v and LM338 linear regulator set at 42.8v for 36v pack = 14.2 per SLA.  Could charge at 2.2 amps and fill battery up in 6~7 hours then hold.  I used 2v higher voltage due to internal resistance placing load and dropping voltage to keep float.  

When input constant voltage is being reached the amps go slowly down from 2 amps to 240ma and holds batteries float at 13.6v.  It worked perfect.

The above DIY charger to test on a real charger read full on the led lights and voltmeter.

Charge intake is really internal resistance depletion until plates are cleaned.

You can charge batteries with 24v if current is low @ 2~3 amps and you take charger off before it gets warm.

Temperature is all important and current limit, the full battery voltage will read higher at high amp charge rate (say 4 amps) and not fully charge, this will trick both charger and the person into thinking battery is full . At high current you then must float charge for a longer time to fill battery to full.


My recommendation amps for SLA battery charging.

1.8 amp current for 12ah
2.5 amps for 20ah
3 amps for 24 ah
5 amps for 40 ah
6 amps for 50ah.

[diverdon]

    Hello All , Thank You for all of the feedback . I am learning ?? I think .. It is somewhat scary to hear the truth sometimes .. I am still not sure if the batteries I have in mind will work but have gotten a Formula from a website or 2 that sorta says yes it will work ..

      volts times amp hours divided by motor wattage is supposto say how long it will run at full speed (Watt Output) ... So

        48volts X 10AH = 480 Divided by 1000 watt motor = 0.48 minnutes at full throttle Right ??

       Thing is I won't be at full throttle all the time plus pedaling plus regen braking .. I think it will work .. might go with 12AH batteries but the weight is it worth it...

     The 1 thing still in my mind and the Question is ... Are these SLA batteries like the model plane/car ones with different "C" ratings or amp output rating . If you put too much of a load on a low C rated battery the volds drop a lot and fast from my experience .. The drop from 48volts to minimum of 24volts for the bike is a rela lot but I still wanted to ask the question ..

     I see many people using SLA batteries and want to do that myself for now as I cannot afford a LiFePo one now and want to get up and running ...

    Once again Thank You for all of the help . I hope to be "One Of You" people with a running bike soon ... Next Week .. Thanks Again ,  Don J.

[e-lmer]

    48volts X 10AH = 480 Divided by 1000 watt motor = 0.48 minnutes at full throttle Huh Right ??

Well, you mean .48 Hours, which is just under half an hour.

I have always been told that you damage the battery by
running at a current above the 'C" rating.

That means a 10AH battery should not be used above 10A.

1000/48 is just over 20Amps.

I don't know if this is true for all SLA batteries, but it's what I have heard.

[GM Brazil]

If you consider the price vs. longevity, the LFP batteries are cheaper!

[Leslie]

How can you say that you can't afford lifepo4 batteries? Do the math. SLA's stink, for so many reasons. Weight, power lag, longevity. They just don't make sense on an e-bike. You''ll regret it.

In many cases this is true.

However my SLA's are designed to run in EV applications.

They weigh 28kgs with all four connected.  But I only weigh 72kg so I figure the added weight is like me being a big guy on a lighter bike.

I live in sugar cane country so I don't see many hills and my batteries are around 40% cheaper.

I have no LVC so I have the option of draining them to the max and they are rated at 300 cycles 100% dod..

They will not up and die over the first problem with a BMS or charger.

And they can deliver 240 amps over 5 second bursts and internal resistance is low for my SLA's, so really slumps arent an issue.

They are rated at 900+ cycles at 40% dod which my usuage is between 40% and 55%, so I might get a 1000 cycles.

Reliability wise a good EV rated SLA has plenty advantages still.

Looking around at prices I would need $900 in my pocket for lithium compared the $400 I have spent.

Many people don't have that sort of cash handy after built an E-bike.

However

Lithium batteries have come a long way over the last 3 years.  The technology is proving more reliable with better bms implementation and the life span is something well worth the expense for the long haul.

I guess what I am saying in all this is there are different applications and different types of batteries to do the job.  For the same price I would bet my life that 12ah lifepo4's with the load I put on my system would of died 2mths after purchase.  Where as for an extra $500AU dollars some 20ah lifepo4's would do me justice.

I have done 30km round trips and pulled 200kgs 15kms up hills on the home run with my 48v 24ah SLA's, this torchure is IMHO out of range of a similar priced 12ah lifepo4 packs ability.

But I am going to get a 24ah lifepo4 pack with my next change.  Even though this will be $600 more then what I spend now, the outlay for my requirements is worth it because this sized pack will satisfy both my usage and the life span should make up for the added expense.

[diverdon]

How can you say that you can't afford lifepo4 batteries? Do the math. SLA's stink, for so many reasons. Weight, power lag, longevity. They just don't make sense on an e-bike. You''ll regret it.

    Hey Bob .. I'm not made of money ... Hows about sending me a lttle if it's so "cheap" to use the LiFePo.. Do The Math ? I looked at my checking account and my bills ... That's the math I do !!
    New 48V 15Ah XPS Pack cost is $ 1,150.00 + $ 131.00 UPS Shipping from Taiwan

      One of the quotes I got . I don't mean to sound like a jack--- but you sorta made me feel like a cheapscate or something ...

      I cannot afford a LiFePo4 right now but would like to get up and running .. I am lucky to have a job where I can pay my bills and even try this .. I would ask you to put yourself in some others shoes before you make your comments ... Thanks .. Don J.

[GM Brazil]

However my SLA's are designed to run in EV applications.

Well, this changes everything... In your case they are really good!

Here in Brazil you only have ch*t SLA's with 200 to 300 cycles, with no specification about the quick burst Amp capacity. They costs like 50% to 60% of the LFP's. So in MY case, they do not worth the money, for MY use, they can't hadle one year of use and wight 4 times more (I'm a big guy, 115kg).

An GM LFP is 5,5kg, the LSA I have here will be something like 25kg to 30kg!!!

My salary as an master degree student is less than US$ 650 (for now... next year I'll be working as an egineer, so.... nice money ), BUT I can pay the LFP divided by several months. In fact I can pay they in less time than the LSA will run out of juice and became trash.

So, in MY case, the LFP really worth it!

[Leslie]

However my SLA's are designed to run in EV applications.

Well, this changes everything... In your case they are really good!

Here in Brazil you only have ch*t SLA's with 200 to 300 cycles.

I hear you loud and clear on this one.


I went through 2 brands and a different model of Ritar to discover exactly this.

Ritar had the RT series and a sub series. In this model called RT there is the EV series. The plates are different, they are heavier and they use a combination of AGM and Gell squished in between the AGM and plate gaps.  They call it mulripple technology.

All other SLA models would lucky to do me 2~3 months and they would slump very badly.

The Ritar RT EV series I ended up with took every punishment I put to them.  I even had a charger not shut off and woke to them hot and fizzing.  They still delivered. I'm sure I hurt them too much and the new ones I got now I have been easier and more carefu to them.

Good LiFePo4 with reliable BMS is still a more fool proof safe solution and really want to jump ship as soon as these babies start to fail me. The new GM LiFePo4 20ah plastic pack battery look pretty neat to me. It would be nice to see some good reviews for them.

[Leslie]

How can you say that you can't afford lifepo4 batteries? Do the math. SLA's stink, for so many reasons. Weight, power lag, longevity. They just don't make sense on an e-bike. You''ll regret it.

    Hey Bob .. I'm not made of money ... Hows about sending me a lttle if it's so "cheap" to use the LiFePo.. Do The Math ? I looked at my checking account and my bills ... That's the math I do !!
    New 48V 15Ah XPS Pack cost is $ 1,150.00 + $ 131.00 UPS Shipping from Taiwan

      One of the quotes I got . I don't mean to sound like a jack--- but you sorta made me feel like a cheapscate or something ...

      I cannot afford a LiFePo4 right now but would like to get up and running .. I am lucky to have a job where I can pay my bills and even try this .. I would ask you to put yourself in some others shoes before you make your comments ... Thanks .. Don J.

Hey it's ok.

Many people are giving you good warnings here.

Many SLA will cost you a lot of money for 2~3 mths if you are not wise in choice.

Many SLA's are not designed to take the punishment an EV takes out on them.  When you hit bumps on the road especially with direct drive hub motors it hurts the plates I think it even moves them in and out pulsing.  This can damage even good brand batteries not designed for this type of application.  So many have lost more money than its worth and this angers people. 

Many SLA's are designed for non inductive loads, EG. standby for lighting, slow wheel chairs or mobility vehicles for the aged that drain slowly over a day, UPS, small solar power set ups and even then flooded cells are preferred..

The money thing is the same with me, and it cost me quite a bit until I got something that could do me justice, and even now I think I would save money having LiFePo4,  It is the initial outlay that is hardest to do.

I have to carry 27kgs of lead on my bike and disable LVC to get good long term usage of SLA's.  Lots of work getting them on the bike in the right spot, build a shunt reg BMS for SLA.

You need to learn a lot to get away with this for good performances.

So do listen to the advice.