Electric conversion

[Richard’s 314-8 60]

45 minutes ago, wh500special said:

I’m not endorsing them since it’s still somewhat new to me, but I have had great luck with the LiTime batteries in boats.  They are a good value.  
 

Li batteries (regardless of brand) have some quirks.  The internal heaters usually are activated when a charger is connected to preheat the battery before charge current tries to push in.  Once a battery is warmed sufficiently, applying a load to it will keep it warm enough to run things effectively even in cold temperature.   I didn’t look up the specifics of your battery, but most (probably all) of them have built-in functionality in their BMS to shut them down when the interior temperature drops below a threshold.   There seems to be some hysteresis between the off/on temperatures, so if you park that in your yard on a cold day and it shuts down it could take some measurable charging time to get it switched back on. 
 

the other thing I’ve noticed on some other battery applications (at work, not using LiTime batteries) using this battery chemistry is that the ability to push a high rate of current drops off

pretty significantly with temperature.  I think they are much more kinetically limited than a lead battery.  We were testing last week at -25F and my specialty  battery that will easily put out 150A at 32F seems limited to about 15A at -25F.  This probabky won’t matter to you other than the point that when it’s cold and your battery is chilled that you’ll probably have plenty of power to drive around without much noticeable performance loss, but it you try to pull a plow or something you might not be able to do it until the battery warms up.  We are cranking an engine with this battery and have to do a lot of tricks to get it to work when it’s done that cold. 

 

 It’s somewhat counterintuitive, but there is a lot to be gained by wasting some power putting a load on them thing for a while to get the battery warmed up before working it.  Once it’s warm, it stays that way pretty easy. 
 

Another quirk is that estimating the state of charge of the battery from its voltage level is all but a waste of time.  A drop of a fraction of a volt at the top end can represent a big decrease in stored capacity.  At the bottom rend, the voltage can hold relatively steady for a long time right up until the limit where the battery shuts off.
 

If getting an estimation of how much power is left in the thing is useful, you’ll need to measure the current in and out of the thing over time.  There are gizmos that do this for you which aren’t cheap.  if your battery has a Bluetooth connection, it probably takes care of state of charge monitoring.  I initially didn’t see the point in having a connected battery, but see it as a nonnegotiable now.  
 

I’d suggest leaving the charger offboard.  No sense subjecting it to vibration and environmental factors if you can avoid it.  An appropriate Anderson connector makes it easy to hook it up.  
 

This summer I might outfit one of the E-141s with Lithium if LiTime puts their 100A-hr 12 volt batteries back on clearance or has the reconditioned ones available again.  Runtime is amazing and unlike a lead acid, you get to use the whole capacity (almost) instead of just half.  On a usable power basis, these batteries are potentially less expensive than lead acid.  Last fall, they had 100 A-hr 12 volt batteries for right at $100 apiece.  It was a steal.  They weren’t Bluetooth, but at that price it’s not out of the question to improvise something. 
 

I’m enjoying your project!

 

Steve

Thank you for all that info Steve. I’m also curious on the solid state battery technology they are working on now. 

[Handy Don 15,620]

10 minutes ago, Richard’s 314-8 said:

Thank you for all that info Steve. I’m also curious on the solid state battery technology they are working on now. 

Me, too!

The last report I read mentioned that Donut Lab has a “production ready” version. I wish I knew what that actually means. 

[Richard’s 314-8 60]

1 hour ago, Handy Don said:

Me, too!

The last report I read mentioned that Donut Lab has a “production ready” version. I wish I knew what that actually means. 

I read that too