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What amperage should I set my DC-DC Charger in the bus?

 
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Hi All,
I’m nearly done installing a “house” battery and charging system in my little 4 window bus. Ive installed a Kisae 50 amp (maximum) DC-DC charger that will accept alternator power when the starting battery reaches a certain voltage. The charger also has solar power inputs and switches to solar automatically if not enough alternator power is available. But I don’t have a solar panel installed yet. The charger amperage is adjustable in 5 amp increments so it is current limiting. I’m concerned about overheating the alternator if I set it too high. I have a stock alternator. I think it’s 100 amp. The battery will be fairly big and power hungry (Nissan Leaf lithium ion) so I want to charge it with enough power but not burn up my alternator. These buses have very poor cooling in the engine compartment and get hot. Ive heard a few people pipe cooling air onto the alternator. Charging while idling for long periods in hot weather is to be avoided I’ve heard as there is little air flow.
I’m thinking of getting a 12 volt heat mat to place under my solar shower bag. I’m not sure what other DC loads there will be yet other than the normal device charging and lights. There is a inverter load.
Is there a easy way to check the temperature of the alternator and engine?
Thanks, Happy Spring!
 
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Just thought I'd share...


https://eugene.craigslist.org/search/gra?s=240



 
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Can you tape a thermocouple thermometer to the alternator?

Charging a half empty car battery at 100A … might take 15minutes. So I would expect the alternator to be designed to handle the full current… And your chargers tops out at 50A, so I'd think it should be safe?

And in hot weather solar panels are probably the better option anyway.
 
Jeremy Baker
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Thanks, I got inspired to install a solar panel today. It’s a 190 watt panel. Not as much solar as I’d like but better than nothing. Will be interesting to see what it produces. The Kisae DC-DC Charger has a display.
Next is to assemble the Leaf battery. I’m thinking of going with a 4S7P configuration. If the batteries were new that would be about 450Ah at 12 volts but the batteries are used so I dont know what the capacity of the is.......if they are 80% capacity it’s 360Ah capacity.
What I dont like is how hot the battery location is. Heat is a killer of batteries. They have more power but croak sooner. They are located next to the engine doghouse of the van. Ive got some shiny Reflectix insulation to try and protect them with. Again, like with the alternator, more air flow would be good.
 
 
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You can probably find detailed info on your alternator, charge curves, heat response, etc on the net. Most alternators today use internal voltage regulators, but there many good aftermarket external controllers which allow you to control your alternator more exactly. If you deem that needed. However, the detail specs on the alternator are important in any case. In the course of finding the specs on your alternator, you will likely find what manufacturers and part #'s provide "bolt-in" upgrades to your alternator if you need more power.

> temperature
Easiest way is an IR thermometer gun from a box store, assuming you can see the alternator easily from above or below. $35-$75. Consider getting the more expensive ones because usually they are much easier to read. Some external regulators have a temperature input which they use to cut back on output when the alternator gets too hot. Another reason for getting the detail specs for your alternator is that most alternator ratings advertise "max" output, not "continuous" output.

And good ventilation would help a lot, but... Hard to get that w/out taking a sawzall to do crude functional things to the face of your be-ay-u-tiful vehicle . <g>   Running the vehicle just to charge the battery is not an elegant solution,  though. Probably not even a good one.  Maybe just open the hood and face into the wind for a bit until you get around to putting your real charge source into place?

> your original Q
Just at a guess, if your charger will limit its input power, it sure looks like less is better to start with: 50 amps or less and see what happens and how the battery charges up in how long. If you get an IR gun, it's pretty easy to monitor things. And they're useful in many other ways. Or just put  your hand on the alternator. "OUCH, Ouch, DAMN that's hot" means it's maybe 140F.  "FUCCKKKKK! ShitFucK! ShitShit! FuckFuck! Sizzling? BLISTERS?" means it's north of 190F.  See, you don't need to waste money on those fancy gizmos! <G:>


Regards,
Rufus
 
Jeremy Baker
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Thanks, those infrared thermometers sounds very useful. Better than a burnt hand lol. The batteries are in place now. Might have it all ready today to test out.
D60FA456-A27A-4A9B-8E2C-842C435DC9BE.jpeg
14 Leaf modules in 4S7P configuration
14 Leaf modules in 4S7P configuration
 
Rufus Laggren
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Hope you keep the news and pics coming for all us out here in the Big Virtual.

Cheers,
Rufus
 
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nice setup... Does the kissae have a programmable charge setting for lithium? Im sure you've read up on it but for clarity for others they have a very different charge profile then the agms typically used with that type of kissae charger... no absorb time and a slightly lower bulk voltage.
 
David Baillie
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there you go, note to self read up on the specs before you write something. Seems it does have a dedicated lithium setting... looking forward to hearing about how it works out...
Cheers,  David
 
Jeremy Baker
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Thanks David. I enjoy building these systems. It’s like expensive toys for big boys. So far so good. I flipped the switch and no smoke lol. Yes, the Kisae has a lithium and power supply mode. I’m not entirely sure yet how well it will work at this voltage, around 12.8- 15.5 volts. Ive been busy getting the water tank, sink, counters, etc that were piling up inside the bus installed and strapped down. Will update soon as I get t programmed and do a test drive.
 
Jeremy Baker
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Update:
This bus energy system is working well but it is not ideal for multi-way energy storage. I can only use a small part, the middle capacity, of these Leaf batteries. As long as the vehicle is driven frequently this is working ok to recharge them. One 190 watt solar panel is helping but slow. I have been cooking with electricity and it’s great to save my propane.
I’m going to wire in the mini fridge. I’m thinking of getting a LVD, low voltage disconnect, for the fridge to protect the batteries.
 
Jeremy Baker
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As far as what amperage to set the Charger it seems my bus serpentine belt is the limiting factor presently . It starts to squeal at 30-35 amps. I have not tried replacing the belt and tensioner yet. When I do I’m going to clean the grooves in the pulleys also. Ive read some people have 160- 200 amp charging. Why would my belt squeal at 35 amps. Any suggestions on how to prevent it are welcome.
Ive load tested the system up to about 1200 watts while cooking and heating water. I haven’t felt any connections getting warm. The batteries were going out of balance but Ive corrected that by using some 12 volt light bulbs to equalize them. The Leaf batteries sat unused for 14 months and maybe they are “waking” up? I don’t have a BMS or battery cell equalizers yet so have been checking the voltage zealously about 6 times per day. On the forums people talk about “bottom balancing” and “top balancing” the cells. I think I “ middle balanced” these cells. Ive only seen one reference to middle balancing before stating it’s a acceptable strategy.
I’m considering buying one of these equalizers. Will it work? Any suggestions are welcome:
https://www.electriccarpartscompany.com/12V-4S-Lithium-Battery-Balancers-Equalizers
 
Rufus Laggren
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> belt squealing

Maybe just treat it like an automotive problem. I'd search first on engine model and alternator rating and "squealing" to see if this problem comes up in "normal life" - if so, that was easy. Otherwise, just wade through the generic problem process on the inet. But if you find hits with the stock setup, then that's not a good sign and means that it might be hard to get any "performance" from the vehicle system w/out significant mechanical changes.

But maybe the tensioner just needs changing...

Good to hear the batteries seem willing to take on the job and the wiring seems happy. That's a solid +++.


Cheers,
Rufus
 
Jeremy Baker
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Thanks, I’ll try replacing everything and see if that fixes it. The belt might be nearly worn out. I can keep the old belt as a spare. Last time I changed a belt, tensioner, and idler it cost $115 in parts. And I didn’t know to clean the pulleys. Any residue affects the belt.
With a ex-school bus it’s tricky to look up the alternator as it might not be stock. As with ambulances, shuttle buses, etc, they often use a different alternator.
 
David Baillie
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If it is a 1/2 inch serpentine belt you will be limited to transferring roughly 1 ro 1.5hp or 750 to 1000 watts hp total to all the accessories. So roughly 1kw or you will get squealing. That is why they went to thicker belts eventually. Can you adjust the charge rate? If I'm not mistaken you will get more amps at idle and less when everything else is using power... power steering, ac, water pump etc ...
 
Jeremy Baker
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I think it’s a full 1” wide serpentine belt. Yes, I’ve been adjusting the amperage. I started at 40 amps, it didn’t like that, then 20, 30, now 35 amps on and off all day today. It doesn’t squeal terribly but enough to be irritating. It’s worse when it’s cold engine.
 
David Baillie
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Jeremy Baker wrote:I think it’s a full 1” wide serpentine belt. Yes, I’ve been adjusting the amperage. I started at 40 amps, it didn’t like that, then 20, 30, now 35 amps on and off all day today. It doesn’t squeal terribly but enough to be irritating. It’s worse when it’s cold engine.

any idea how old the belt is? Tensioner and new belt as mentioned above. There is a belt resin they sell for squeaky belts. Might be good for a try to see if you can get more amps with more friction then judge if it's worth changing belts.
 
Jeremy Baker
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Ive had the bus 1.5 years and this belt was on it when I got it. No idea how old it is. It’s topping the priority list now. I wasn’t aware of belt resin?
 
David Baillie
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Jeremy Baker
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Well the 50 amp inline Maxi fuse I bought on eBay melted. I forgot to fasten it down properly and it vibrated loose. Once it was loose the extra resistance caused it to heat up and the plastic melted.  Taped it back together and turned it down to 25 amps. Otherwise I’m happy with the charger and energy system.
I ordered a Electrodacus BMS system to monitor it.
 
Jeremy Baker
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Taping the Maxi fuse in place only lasted a day before smoke started coming out. So I went to Napa and found a automatic resetting breaker. If it trips it tries to reconnect after 10 seconds. It has nuts and studs  so I can bolt lugs onto it unlike the maxi fuse which has blades. Ive turned the dc-dc charger up to 40 amps now and it’s working good.
The solar function of the Kisae DC-DC Charger is working well. Ive seen 11 amps from one 190 watt panel. That’s 150 watts at average of 14 volts.
 
Are we home yet? Wait, did we forget the tiny ad?
Rocket Mass Heater Plans: Annex 6
https://permies.com/wiki/138231/Rocket-Mass-Heater-Plans-Annex
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