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 > generator and alternator charging at the same time

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BFL13

Victoria, BC

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Posted: 04/05/21 06:59am Link  |  Quote  |  Print  |  Notify Moderator

Errin says also they are looking at a new power centre, don't know what converter it would have.

I guess calling a converter an LFP one is just for the "Sales" people, since the LK model already can do any LFP spec plus any other type of battery's specs.

if you can answer the last set of questions and try out the other "set" of converter-battery, then Errin could read all about it here (a link to this thread by email) and do whatever needs to be done.

The converter has nothing in it that can cut out and cut back in that I know of. It has a 120v fuse. Other things in it can fry.

OTOH, the BMS can do that action I think. IMO the first thing is to find out if possible if it is the BMS doing it or not. If it is with the batt you have but not the other batt, then that might be a warranty item for that batt. Maybe that converter is duff, but the other other one is not.

#8 is too skinny for the 55 amper. Could be why only 50 amps. I use #4. #8 has the ampacity in theory but I had fewer amps with it, and good amps with the #4.

* This post was edited 04/05/21 07:13am by BFL13 *


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dave17352

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Posted: 04/05/21 09:45pm Link  |  Quote  |  Print  |  Notify Moderator

8 is good for a 1 foot run. Also the converter has over current protection. Perhaps that is what is cutting the power. The battery handles 90 amps from the alternator no problem.


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BFL13

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Posted: 04/05/21 10:10pm Link  |  Quote  |  Print  |  Notify Moderator

Can you describe in more detail what happened when it "cut out"? Did the converter and battery just sit there with no current flowing all of a sudden (on what meter?), but the 120v to the converter was still on ok?
Was there still voltage at the converter's DC terminals but no amps flowing?
Do you get a read-out from the BMS anywhere that showed something like a code that means a particular thing? What did you do after to get it all going again? The converter didn't fry anything or it would not work again.

The converter is "current limited" but there is no actual over-current protection that shuts it down AFAIK. Are you suspecting a "surge" of current because of the low R of the LFP? You can fry the input thermistor with a surge but that makes smoke and flames (BTDT ! exciting! [emoticon] )

With the 90 amps from alternator, were you able to see what voltage the BMS was seeing at the time? Was it lower than the converter's voltage?

--Trying to figure this out as an interesting mystery, plus maybe have more info to pass to Errin if you haven't already. Tomorrow is a working day so they might be able to look into it.

MEXICOWANDERER

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Posted: 04/05/21 10:20pm Link  |  Quote  |  Print  |  Notify Moderator

Don't forget to factor terminals studs and connections into total resistance. A good way to discover reactive resistance is with an IR gun. LOAD for 10 minutes then scan. Warmer specifics should be examined and rectified. Anything made of brass should be treated with suspicion.

pianotuna

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Posted: 04/05/21 10:42pm Link  |  Quote  |  Print  |  Notify Moderator

dave17352 wrote:

Also the converter has over current protection. Perhaps that is what is cutting the power. The battery handles 90 amps from the alternator no problem.


Did you run wire directly to the alternator? What size wire? What size fuse?


Regards, Don
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Freep

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Posted: 04/06/21 11:38am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:


As the battery voltage rises from being charged, amps will start to taper from the lowest voltage charger of the three until amps get to zero when the voltages are the same, then amps will be tapering on the next highest voltage charger until battery voltage rises to its voltage, and now only the highest voltage charger is supplying amps (to its current limit).


Keep in mind that with LiFePo4 batteries the charging curve is mostly flat. So your battery will stay at 3.3v for a very long time until it hits the knees and then it will shoot up. This is why a BMS is critical. Also LFP batteries in general will take a 1C charge, though some take 3C.


So it's not really a taper. It's more like a firehose and then suddenly(from a voltage perspective) your battery is full.
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BFL13

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Posted: 04/06/21 12:49pm Link  |  Quote  |  Print  |  Notify Moderator

Right, so it is still about the various voltage diffs between the chargers and the battery, but with LFP as long as they are all above the flat part of the voltage, each will all add some of the total amps in proportion to its voltage difference.

The lowest will not drop out so soon since the battery voltage is not going to rise up and pass its voltage so soon like with FLAs.

3 tons

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Posted: 04/09/21 09:45am Link  |  Quote  |  Print  |  Notify Moderator

You might consider a inverter-charger, LFP compatible with 100 (or more...) charge amps - problem solved...

3 tons

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