Adjusting BMS Battery Charger Cut Off Voltage

[jase1979]

Hi,

I have a new battery and want to use my old charger from BMS battery. My new battery is 14s, to requires a voltage of 58.8V.

I previously had a 12s setup. I found out that the voltage on these charger can be adjusted via a trim pot, however my charger maxes out at 56V.

Can I modify the charger, trim pot or near by resistor to increase the voltage to 58.8V?

Thanks in advance

The charger is similar to this photo inside:

 

[john61ct]

56V ÷ 14S = 4.0Vpc

if you don't mind sacrificing a bit of range, that would certainly be good for longevity.

How much lower the SoC, will depend on how long the charger holds Absorb/CV stage, won't sacrifice much at all if it holds until trailing amps fall lower than 0.01C,

if it just charges **to** 56V and stops (CC / Bulk stage only, no CV) then you may have 10-15% lower range or so,

CC-load discharge testing using a precise timer will tell you precisely, don't trust an Ah counter.

Another caution, running a cheap charger at the maximum voltage it can be trimmed to, may be stressful enough to shorten its lifespan.

And you will need to find another way to get cell balancing done, adjustable BMS, a balance charger or other non-BMS balancing gear.

 

[jase1979]

Thanks for the reply. Yes I was concerned about the BMS not balancing the cells. As I've read that most of the BMSs don't start to balance until 4.2V.

 

[john61ct]

You could overcome that problem most easily by getting a charger that is easily voltage-adjustable.

So going to vendor-spec over-voltage for balancing purposes could be an explicit occasional maintenance routine, like old-school equalizing a lead bank.

Or even better, a BMS with both an adjustable start-balance voltage, and

a decent balancing-bleed current rate, certainly over 1A, ideally say 6A.

Another alternative is exposing the per-cell (parallel group) connections to external "balance leads", and using a "hobby" balance charger to get a perfectly balanced charge every cycle at whatever termination voltage you like.

Your choices of quality chargers would be a lot wider splitting that 14S with a midpoint tap for the bulk-charge leads, in effect two 7S packs in series.

And finally, there are dedicated balancer gadgets that can be run as needed, at whatever layout, whatever voltage, in theory could be hooked up to work at all times.

 

[TommyCat]

Another caution, running a cheap charger at the maximum voltage it can be trimmed to, may be stressful enough to shorten its lifespan.

+1

A voltage increase such as this may reduce the amperage capabilities to near half. Use the wattage and math...
But I see the other two pots peeking out, and this too could be adjusted. Take a close look at this thread for tips on operation and adjustments of chargers...

https://electricbike.com/forum/foru...-to-adjust-the-luna-charger-mini-and-advanced

My advice would be to get a proper charger for your new nominal voltage that has settings for 80,90, and 100% charging capabilities.

Example... https://lunacycle.com/52v-3amp-luna-mini-charger/


Regards,
T.C.

 

[john61ct]

Relevant other thread
https://endless-sphere.com/forums/viewtopic.php?t=101750

 

[john61ct]

Grin also makes Satiator, great adjustable chargers

https://www.google.com/search?q=site%3Aendless-sphere.com+grin+charger

 

[999zip999]

Are those 63v caps ?

 

[jase1979]

This is my actual controller, the earlier image is a similar controller.

https://drive.google.com/open?id=1wZwlmoaP7RaFRsjNFAO6ZaxUQTtAb7ZQ

 

[jase1979]

Apologies, I meant charger.

 

[jase1979]

Maybe I should have changed the title. The charger I have is from the website called "BMS Battery". So this post is nothing to do with the BMS as such.

I want to adjust the charge voltage output for 14s. I can only get it up to 56V. The trim pot has then reached its limit. Is there anyway I can increase the voltage? I've seen a few threads of people increasing the voltage on his style of charger. They seem to have a much greater ranger.

Thanks again for all the previous replies.

 

[john61ct]

Likely not, either upgrade or look at DC-DC converters, might cost even more.

But the good news is that voltage, 4.0Vpc is perfectly fine for 14S, in fact will greatly increase longevity without losing much range at all.

But you need to make sure per-cell balancing's getting done, one way or another.