Generator battery voltage issues

[justinm001]

My 20kw genset in my RV has a dedicated battery which I replaced with a Optima D31m bluetop. I also removed a huge 240v fan in a squirrel cage and replaced it with 2x80w 12v fans. The genset seems to have a very small alternator and can't handle the load, so I added one of those htrc 20a charger plugged into my house system which is left on all the time to keep the thing topped off. Problem is the generator control panel has weird issues when the charger is running, saying the voltage is like 15.4V and then the temp sensor will show very low like 15 or 40 degrees when its really like 180 degrees. If i turn off the charger all is good but then the voltage drops low because of the fans.

On top of this I decided to wire up my tank and battery heaters up to this battery. I also decided to replace the little charger with a large 100a Powermax charger https://a.co/d/e1KV0Hp How should I program this charger? Just leave it at a specific voltage (what voltage) or put the 3 stage part on?

I believe the battery charge is recommended at 30a. 4 65w tank heater pads (21a) plus the 160w in fans (13a) and it also has another oem radiator 12v fan. Once winters over I'm not sure if I should leave this on or switch to a trickle charger.

The other issue is the fans only come on when the generator is on (using relay) I don't think the fans are strong enough to keep it running so if I ever use the genset I plan on just running for 20 minutes with a 20 minute break but running the fans to cool off then start it back up if needed. I'll program this with Victron to auto start at 20% battery then off at 40% which should be around the 20-30 minute mark.

 

[0truck0]

Not undrstanding fully...

Your gen starting battery is only for starting, it is not meant to power the "house".
Do you have dedicated house batteries?

Generators generate alternating current very well. Most only generate a little bit of DC current, meant to top off the starting battery, not to charge a bank of batteries or to run high DC loads. Confirm what your generator does?

Most RVs have gens that power a charger/converter for the battery, house/coach battery. The charger is plugged into AC current, not DC. The converter portion turns the AC into DC and that is what runs the DC stuff in the house/coach/RV.

The house batteries will run the RV when no generator or shore power is available, for a while.

IDK why you would replace AC fans with DC fans, not for this large of a fan. The generator is for AC loads.

Is this going in your house house or in your RV?

 

[justinm001]

Not undrstanding fully...

Your gen starting battery is only for starting, it is not meant to power the "house".
Do you have dedicated house batteries?

Generators generate alternating current very well. Most only generate a little bit of DC current, meant to top off the starting battery, not to charge a bank of batteries or to run high DC loads. Confirm what your generator does?

Most RVs have gens that power a charger/converter for the battery, house/coach battery. The charger is plugged into AC current, not DC. The converter portion turns the AC into DC and that is what runs the DC stuff in the house/coach/RV.

The house batteries will run the RV when no generator or shore power is available, for a while.

IDK why you would replace AC fans with DC fans, not for this large of a fan. The generator is for AC loads.

Is this going in your house house or in your RV?

Yes dedicated house LFP batteries with inverters and everything else.
I also have a dedicated generator battery. Meant just to start the generator.

The generator came with the rv, it's pretty standard in Prevosts. But the coach is designed to run the generator all the time so had a massive squirrel cage fan that was about 3x3x3ft and wasted a TON of space. I assumed since it already has 1 DC radiator fan so adding a couple more wouldn't be an issue. Removing that fan easily fit both my Quattro 5k inverters and 2 rack batteries, could fit 2-4 more even.

Since I have massive batteries, inverters plus solar and dc-dc chargers there's no real need for the genny. And if I have a need for long term usage to power my house or something I have a large AC fan and can open the bay door.

The problem is I don't know why the genset would show the voltage is high with an additional DC charger and how it'll mess with the temp sensors and anything else?

Also I don't know what to set this bigger charger to. I have it plugged in but haven't tried the genset yet.

Adding the tank heaters to the 12v genset battery just gives me a big battery backup for them, since that battery is plugged into my AC house system so if my house batteries die then it'll run off the genset battery.

 

[ElectricIslander]

Yes dedicated house LFP batteries with inverters and everything else.
I also have a dedicated generator battery. Meant just to start the generator.

The generator came with the rv, it's pretty standard in Prevosts. But the coach is designed to run the generator all the time so had a massive squirrel cage fan that was about 3x3x3ft and wasted a TON of space. I assumed since it already has 1 DC radiator fan so adding a couple more wouldn't be an issue. Removing that fan easily fit both my Quattro 5k inverters and 2 rack batteries, could fit 2-4 more even.

Since I have massive batteries, inverters plus solar and dc-dc chargers there's no real need for the genny. And if I have a need for long term usage to power my house or something I have a large AC fan and can open the bay door.

The problem is I don't know why the genset would show the voltage is high with an additional DC charger and how it'll mess with the temp sensors and anything else?

Also I don't know what to set this bigger charger to. I have it plugged in but haven't tried the genset yet.

Adding the tank heaters to the 12v genset battery just gives me a big battery backup for them, since that battery is plugged into my AC house system so if my house batteries die then it'll run off the genset battery.

I'd rethink that fan replacement, or at least run the numbers and check your work before thermodynamics checks it for you.

The aerodynamics and other aspects of fan design are very specific to each application. Squirrel cage fans are very high capacity. Are you sure that this large a fan is not not needed to deal with the large amount of waste heat from a 20 kW gen set. At about 30% fossil fuel internal combustion thermal efficiency, that means that around 60 kW of waste heat is released by a 20 kW generator when running full tilt. Although much of this heat goes out the exhaust pipe, there is still a lot of heat coming out of the casing of a 20 kW gen set that has to be ventilated away.

Not sure what you meant by "I assumed since it already has 1 DC radiator fan so adding a couple more wouldn't be an issue". Vehicle radiators get by with flat pancake DC fans because the airflow path is really short. Ventilating your generator compartment is not the same type of design challenge as moving air through a radiator. Are you matching the cubic foot per minute (CFM) rating of the old squirrel cage fan with the new fans? Are the new fans designed for the same back pressure rating and velocity as the old fans?

I'm speaking as a design engineer that burned up one of my own generators by running it in a poorly ventilated box ....... beware!

 

[justinm001]

I'd rethink that fan replacement, or at least run the numbers and check your work before thermodynamics checks it for you.

The aerodynamics and other aspects of fan design are very specific to each application. Squirrel cage fans are very high capacity. Are you sure that this large a fan is not not needed to deal with the large amount of waste heat from a 20 kW gen set. At about 30% fossil fuel internal combustion thermal efficiency, that means that around 60 kW of waste heat is released by a 20 kW generator when running full tilt. Although much of this heat goes out the exhaust pipe, there is still a lot of heat coming out of the casing of a 20 kW gen set that has to be ventilated away.

Not sure what you meant by "I assumed since it already has 1 DC radiator fan so adding a couple more wouldn't be an issue". Vehicle radiators get by with flat pancake DC fans because the airflow path is really short. Ventilating your generator compartment is not the same type of design challenge as moving air through a radiator. Are you matching the cubic foot per minute (CFM) rating of the old squirrel cage fan with the new fans? Are the new fans designed for the same back pressure rating and velocity as the old fans?

I'm speaking as a design engineer that burned up one of my own generators by running it in a poorly ventilated box ....... beware!

I was talking about the alternator load adding 160w in additional fans wouldn't be an issue.

I don't plan on using the genset and if I do I only need it for short period of times, so enough for it to heat up then I can turn it off and let it cool down before running it again. I'm not sure if it's safe to run a diesel engine only 15 minutes at a time but seems to work fine. Basically the temps would get up to opening the thermostat then I'd shut it down but leave the fans running and it'd cool down. When I tested it I was able to run 15 on 15 off for a couple hours and the temp sensors were under 180. The genset screen has a coolant temp and I put a ruuvi temp sensor on the top of the radiator.

With the squirrel cage it would pull air from the front bottom of the generator bay, through the engine and through the radiator mounted in the rear before blowing it out the other side of the bay. Now it's just sucking air out of the front bottom of the bay.

If I ever do need to use the generator for long periods of time I have a massive fan I can bring and open the bay door.

I tested this without the fans and the genset would get close to 200 in 10 minutes. The fans definitely help. Imma grab my flir and I just got a cfm flow meter so will do some further testing to see how well this setup works and how long I can leave it on without it shutting down for over temp.

 

[Checkthisout]

Current ripple from your second charger. Get a better quality charger.

 

[justinm001]

Current ripple from your second charger. Get a better quality charger.

Thank you this is what I thought so swapped with the powermax, just not sure what to set it to. I'm thinking single stage like 13.5v so it'll keep the battery pretty charged but use it for all the 12v loads.

 

[Checkthisout]

Thank you this is what I thought so swapped with the powermax, just not sure what to set it to. I'm thinking single stage like 13.5v so it'll keep the battery pretty charged but use it for all the 12v loads.

13.2 on the voltage or "float" which might be a bit higher.

I assume your starting battery is still Lead-Acid. (I think you said above).

For winter, as long as there are not any draws, I would just set the charger to 14.4 and power it up for like an hour once a month to stir the battery. Maybe even less frequent.

This an old bus with a Detroit?

 

[justinm001]

13.2 on the voltage or "float" which might be a bit higher.

I assume your starting battery is still Lead-Acid. (I think you said above).

This an old bus with a Detroit?

This is only generator battery which is the optima blue top.

The starting batteries are 4x12v in a series/parallel 24v and only used for engine. It's an 08 Detroit S60 12.7 chassis engine

 

[Checkthisout]

This is only generator battery which is the optima blue top.

The starting batteries are 4x12v in a series/parallel 24v and only used for engine. It's an 08 Detroit S60 12.7 chassis engine

Right. I meant generator starting battery, not main engine.

 

[justinm001]

Gotcha, I'm confused in how chargers work especially with lead acid and loads. I want the battery to be at 100% all the time and any additional loads to be pulled from the powermax, except when the generator starts as its a massive load. If I set the voltage to 13.7 and have no loads then ideally the powermax wouldn't be doing anything, thus close 0 consumption, right? but if it has an idle load of 50watts or something then seems pointless to leave it on other than when freezing (for tank heaters). I have a few 800ma trickle chargers, maybe I need to keep those running instead.

Problem with some trickle chargers is for some dumb reason they have a light or something else drawing a parasitic load when not plugged in, so if I leave it plugged into the battery but not into AC then it's just slowly draining the battery.

I have the same question with my 24V chassis batteries. The coach came with a 28.5 or so powermax AC to DC charger which I've left on for past couple months.... but now seems it died so likely going to replace it. Ironically its placed right in the generator bay for some odd reason. There's been times where we've left the key to on and like the idea that it'll just use AC when that happens.... for some reason we need the key to on so we can operate the slides so we turn the RV off then the key to on then move the slides and forget to turn it off.... we need to add a dinger thingy.

Ideally when I have shore coming in or solar coming in I'd want it to charge the chassis and gen batteries then when its lost they're all on their own. I have a ton of smart switches so ideally when I figure out what devices to charge and how to properly set them, I can figure out how to get Victron to tell the switches to turn on. Run everything on automation then some redundancy to make sure its at the proper voltage

 

[Checkthisout]

Gotcha, I'm confused in how chargers work especially with lead acid and loads. I want the battery to be at 100% all the time and any additional loads to be pulled from the powermax, except when the generator starts as its a massive load. If I set the voltage to 13.7 and have no loads then ideally the powermax wouldn't be doing anything, thus close 0 consumption, right? but if it has an idle load of 50watts or something then seems pointless to leave it on other than when freezing (for tank heaters). I have a few 800ma trickle chargers, maybe I need to keep those running instead.

Problem with some trickle chargers is for some dumb reason they have a light or something else drawing a parasitic load when not plugged in, so if I leave it plugged into the battery but not into AC then it's just slowly draining the battery.

I have the same question with my 24V chassis batteries. The coach came with a 28.5 or so powermax AC to DC charger which I've left on for past couple months.... but now seems it died so likely going to replace it. Ironically its placed right in the generator bay for some odd reason. There's been times where we've left the key to on and like the idea that it'll just use AC when that happens.... for some reason we need the key to on so we can operate the slides so we turn the RV off then the key to on then move the slides and forget to turn it off.... we need to add a dinger thingy.

Ideally when I have shore coming in or solar coming in I'd want it to charge the chassis and gen batteries then when its lost they're all on their own. I have a ton of smart switches so ideally when I figure out what devices to charge and how to properly set them, I can figure out how to get Victron to tell the switches to turn on. Run everything on automation then some redundancy to make sure its at the proper voltage

Just go with a DC to DC converter for your 12v stuff

 

[justinm001]

Just go with a DC to DC converter for your 12v stuff

No it's a single point of failure. All my 12v stuff is ran on 2x400ah lfp batteries and charged using a Quattro 5k inverter which handles aux loads. It's just the tank heaters that'll run off the gen battery which I feel is better because it's redundant.

Shore charges 48 system which charges 12v system which charges gen battery through inverter which keeps tank heaters warm. If my 12v lfp system dies it'll use the gen battery to keep warm until that dies. If I'm there I can just plug that AC cord into the 48v inverter outlet in the bay.

If I'm boondocking for a long period of time I can just hit the smart switch and shut off my gen battery charger. But in winter this isn't much of an option since it uses tank heaters. Idk how many ah the battery is vs how much power the tank heaters need to keep them warm.