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Old 09-12-2022, 06:23 PM   #57
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[Mod Edit]

It seems the link I sent failed somehow.
1) If anyone wants information on RV power, dual alternators, direct alternator charging, lithium batteries, Mini-split A/C, hydronic heating, water purification/recirculation, etc...lots of technical topics, first see: YouTube.com/WorkingOnExploring and look at the number of videos we have produced on various technical topics including the building of our Adventure Truck;
https://YouTube.com/WorkingOnExploring/
2) For technical documents I have written, see; https://workingonexploring.com/techdocs/
3) For information on my 'Alternator Thermal Overload Safety' device, (try this again)
https://workingonexploring.files.wor...protection.pdf
4) If you want personal help, contact me through my profile infomation.
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Old 09-12-2022, 07:59 PM   #58
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Originally Posted by MechEngrSGH View Post
404 File not found
It seems the link I sent failed somehow.
1) If anyone wants information on RV power, dual alternators, direct alternator charging, lithium batteries, Mini-split A/C, hydronic heating, water purification/recirculation, etc...lots of technical topics, first see: YouTube.com/WorkingOnExploring and look at the number of videos we have produced on various technical topics including the building of our Adventure Truck;
https://YouTube.com/WorkingOnExploring/
2) For technical documents I have written, see; https://workingonexploring.com/techdocs/
3) For information on my 'Alternator Thermal Overload Safety' device, (try this again)
https://workingonexploring.files.wor...protection.pdf
4) If you want personal help, contact me through my profile infomation.[/QUOTE]

Thanks for the link!
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Old 09-12-2022, 11:51 PM   #59
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Is frying the alternator something that I need to worry about.
You can't control anyone's worrying. Worry is what sells the idea that 25A-40A is all you will need to charge your lithium bank. So it pretty well keeps Victron and the others "in the money". If you monitor your alternator temperature and amps, the worry will end as you determine what you honestly need and what your true exposures are. Otherwise it's just a social media shouting match about what you have, what you need and what's going to happen, when, with who and how.
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Old 09-13-2022, 12:30 AM   #60
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Early this year, I moved 300ah to my toad - to power a fridge/freezer while offroading. And that alternator charge rate has not passed 70a per my observation.
I take it you are in charge of all the food for the group picnic?
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Old 09-13-2022, 03:59 AM   #61
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I take it you are in charge of all the food for the group picnic?
300ah does provide plenty of juice to burn. Next time if you go offroad near us, (for exmple Bisti NM), you are invited .

A full charge can run the fridge for 3 days. But once engine is started, it gets charged up quickly.
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Old 09-14-2022, 06:07 PM   #62
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You can't control anyone's worrying. Worry is what sells the idea that 25A-40A is all you will need to charge your lithium bank. So it pretty well keeps Victron and the others "in the money". If you monitor your alternator temperature and amps, the worry will end as you determine what you honestly need and what your true exposures are. Otherwise it's just a social media shouting match about what you have, what you need and what's going to happen, when, with who and how.
WELL SAID!

While most DC-DC chargers are in the 20-40A range, the primary reason is that manufacturers KNOW most users don't have more capacity than that and they don't want to be blamed for frying alternators (although some still will).

It irritates me to no end to see how unfamiliar people are with the meaning of an alternator rating (is a means of comparison, not what you will get in your vehicle).

So many conditions change when driving, the ONLY WAY to protect yourself is to 1) monitor alternator temperature and 2) have a means to cut off your optional load (safely) when it overheats.

The absolutely minimal effort it would take for B-B manufacturers to add a thermal shutoff, like I have made, to their product boggles my mind.....They probably don't want to make the customer aware that by using this B-B, they are pushing the envelope on alternator overload....
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Old 09-14-2022, 06:30 PM   #63
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What about adding a alternator protector to protect against damage from BMS shutdown.Click image for larger version

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Old 09-15-2022, 12:33 AM   #64
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What about adding a alternator protector to protect against damage from BMS shutdown.Attachment 376402
Little background; 20 years ago, I designed a warehouse portable powered cart designed to move a computer and printer around distribution center warehouses to conduct transactions and label printing. The primary customer was a WalMart grocer in the UK called Asda but current customers are ALL of WalMart, Nordstrom, Target, Lowes, Home Depot, Catapillar, and others I forget. I had the luxury of designing after another company created a failure nightmare BUT the key was to build a 'self-defending' controller (akin to a BMS although these were 2-100Ah sealed LA) that prevented ignorant operators from doing things to the system that killed the batteries.

Just as there is a right way and a wrong way to terminate charging, there is a right way and a wrong way (IMHO) to design a BMS. Those of you with 'drop-in' replacement batteries are victims of the battery manufacturers who want the easy sell and give you a BMS with a guillotine when a feather is needed. The way they terminate charge can be destructive without option. They do this for their own protection but convince you they are doing it for yours.

The right way to terminate charging is to tell the charger to shut off, not to cut the power leading to the battery. With this in mind, the responsible BMS will have output switched outputs that can be used to tell the charging source to shut off while all battery power continues to be available. Its incumbent on the user to set the BMS up to work properly with their charging (and discharging) sources for safe battery operation. I refer to drop-in replacement batteries as 'batteries for dummies' and it is not without cause. Not trying to offend but lithium is a new ball game in both potential and responsibility. Most LA batteries ever made were destroyed by their (ignorant) users. BMS may prevent that with lithium but the ignorance is still there.

I use an Electrodacus BMS0 (see Electrodacus.com). This BMS is about the size of a deck of cards and the front is a color LCD screen. It has the ability to measure battery current, solar charge current and diversion load current and displays all information on the screen as a good battery monitor would. It has 4 solid state relay (SSR) outputs that can be set to different conditions when Max or Min conditions are met. For my chargers (alternator, inverter, solar), output to 3P2T relay with a line to each charger that, on the BMS signal, tells each of these devices they are either 'OK to charge' or not. Similarly, another SSR is connected to my inverter telling it 'OK to invert' or not. When the battery voltage gets low, it tells the inverter to turn off. I do this at a voltage higher than the absolute minimum so I still can operate small DC things like lights. I know that manufacturers are working for products for the masses and that in order to move volumes, they need to avoid trying to train users....those of you on this forum are at least smart enough to know what you don't know.

I love Charles Sterling. He makes good products. What you don't know is that your alternator contains avalanche diodes that do much of what this product does. If you need more, Littlefuse sells unidirectional 'Transient Voltate Spppressor' (TVS) diodes that do this for a couple bucks....
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Old 09-15-2022, 12:45 AM   #65
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I misfired....think of these as a 'pressure relief valve'. Use a voltage about 30% higher than your maximum anticipated voltage and use that. Place the TVS between power and ground. It will only begin conducting when the voltage exceeds the device rating and shunt the excess voltage to the ground. If it is a high power source, you can gang multiple in parallel to handle larger amperages. They are bi-directional so they don't care which direction they are installed. This is essentially what diodes in your alternator already do. The diodes in your rectification bridge are called 'avalanche' which means they can conduct in reverse without being damaged. They conduct in a forward direction at ~.5V and in reverse at about 20-25V.

https://www.littelfuse.com/media?res...-5kp-datasheet
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Old 09-16-2022, 01:22 AM   #66
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2000 watts on 12vdc is 166 amps, or 50%= 83-amp; mOST YOU DESIGN TO RUN AROUND 50%; my Class-C options are 95a or 130a alternator; if battery down from boon docking, you should shutoff INVERTER and charge batteries FIRST, and install AMMETER and maybe 120vac METER, too, so that you can monitor ALTERNATOR LOAD AND INVERTER OUTPUT STATUS/ VOLTAGE and while driving? This could be effective and safe, if you wait until OTHER loads= down before starting INVERTER/ REFRIG? WHAT is your REFRIG LOAD/ Features; the old LPG Refrig was only about 200-250watts in electric heater mode?
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Old 09-17-2022, 12:41 PM   #67
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I have a 2004 Itasca Horizon 40KD. I have 4 battleborn lithium 12 volt coach batteries. I do not have a Battery Isolation Manager or DC to DC charger. My alternator quit on me and had it replaced to the tune of $1,000. The new one is now also toast a month later, I am quickly figuring out the alternator is overheating on long drives.

I need to get a BIM or DC to DC charger obviously. But in the meantime, can I disconnect all but one coach lithium battery to avoid overheating the alternator? Any suggestions on what I can do in the meantime? I have some long trips scheduled and deadlines to meet.

Thanks in advance!
Couple more thoughts back on the original topic;
1) NEVER disconnect batteries in parallel...NEVER, NEVER. In order to place batteries or cells in parallel, they need to be within about 10mV of each other or there will be a massive discharge from the high battery to the low battery when connected. If you were to disconnect them, you would have to carefully charge them to the same voltage to be able to reconnect them.
2) Understand what the BIM does. It is essentially a relay that connects the auxiliary batteries to the vehicle batteries for 15' to charge then disconnects them for 20' to allow the alternator to cool off. There is no consideration for ambient temperature, alternator capacity, vehicle load, driving conditions or the load dump that occurs when it shuts off (which would be very significant with 400Ah). It does not limit current draw, it does not sense or limit alternator temperature. It 'guesses' that the overload that will most certainly result from connecting the massive load to the alternator will not occur in 15' and doubles down on that by 'guessing' again that the alternator will cool sufficiently in 20' (it probably will. How do I know what happens? I have instrumentation on both my alternators for voltage, amperage, and temperature AND I directly manage the charging amperage to my batteries that allow me to trim charging to prevent overheating (120C) amperage to achieve a steady temperatue. I am very familiar with what stable and sustainable conditions look like. While a BIM, under circumstances, may be fine, under other circumstances, it won't be. While few of you are likely able to do what I have done, I want to advise you to do enough instrumentation to understand your situation before you pick a solution and 'hope for the best'. I can tell you from experience, that there are so many variables affecting amperage and temperature, that without some way to measure temperature and manipulate the current, you are likely to be entering potentially destructive charging without it. There are some clips of my console instrumentation on my instagram @maximus.4x4.camper.

The bottom row shows my '24V' battery charging at almost (bottom left) 3kW (101A @ 28.8V) coming from a 220A alternator at 229F (bottom right). At the bottom right you can see the edge of the alternator regulator output control adjustment that I can use to dial up or down the output and watch the temperature respond.
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Old 10-17-2022, 06:03 AM   #68
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I am far from

Alternatives. Disconnect the bridge circuit. Only charge the lithium bank using generator or shore power. Many owners settle on this as a permanent solution.
I choose that method as alt too critical to rv. My bridge between alt charging to liths is just one 5 amp fused now removed.
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Old 10-18-2022, 02:15 PM   #69
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I choose that method as alt too critical to rv. My bridge between alt charging to liths is just one 5 amp fused now removed.
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You could also apply that argument to engine or transmission climbing a mountain pass. You get to the point if you don't use it you lose it.



For pedestal to pedestal camping and with a B2B 40A alternator charge rate the only option for most, I can finally the see the reasoning regarding alternator charging going the route of "why bother". And with the B2B salesman with their small servings, I do chuckle when the response of many is to "just keep it".
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Old 10-19-2022, 09:56 PM   #70
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Our 210 amps of lithium were down to 10% recently. It was dark at our campsite so no solar. Also our Onan 5500 was shutting down after a half hour or so. We have a 12v refrigerator that was using significant energy because of the ambient temperature which was in the mid 80s at 6 PM when we got back to the motorhome. So pretty warm in the motorhome. Our only option was to use the motorhomes alternator to charge the batteries.

At 10% charge, they were thirsty. After starting the engine, our battery monitor was showing a charge of between 70 and 80 amp hours going into the batteries. I was concerned about the alternator overheating so only ran the engine for about 10 minutes before shutting it off for maybe 15 minutes. Over a 3 hour period we were able to get the batteries to about 50%. Pretty sure we didn't do any damage to the alternator during that period.
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