โNov-07-2021 04:18 PM
โNov-08-2021 08:10 AM
โNov-08-2021 07:06 AM
pianotuna wrote:
Being a class C person--under the hood = heat. *wiping the egg from my face*
I will never own Li batteries (unless Lithium Titinate drops in price), because I camp at -30.
Is there a reason to not use the OEM battery compartment?
โNov-08-2021 06:41 AM
โNov-08-2021 06:32 AM
pianotuna wrote:
Teleman,
You Li batteries will not "like" life under the hood.
DC to DC are not happy about under the hood either.
I have a similar alternator. I deliberately chose a 20 amp DC to DC unit from Renogy.
If I were buying again, I might go to 40 amps, but only because it has a "link" that when removed puts it back down to 20 amps.
https://www.renogy.com/12v-20a-dc-to-dc-on-board-battery-charger/
Victron makes a similar more expense (but probably more reliable) unit.
โNov-08-2021 06:24 AM
โNov-08-2021 06:04 AM
Teleman wrote:otrfun wrote:Teleman wrote:A BMS is not designed to function as a charger. It is designed as final line of defense to protect the battery.
I ordered a 200AH LifePo battery to replace my two 100AH lead acid batteries and also a compatabile converter which takes care of charging the battery with shore or generator power but what about charging the battery with the alternator? Does the battery's BMS take care of everything and therefore no need to change or upgrade the alternator? Sorry if this is a dumb question!
If you're counting on the wiring to/from the alternator to limit current between your alternator and batteries, you're going to have to choose the proper gauge wire or cable. Too big (physically), may allow excessive current (potentially overloading both the alternator and/or battery). Too little current will result in excessive charge times. There's no magical chart that's going to give you a precise answer. If you've priced copper wire lately, a trial and error approach could get very expensive. Also, if you change size/type of batteries in the future, you'll need to current match the wiring again.
That's one of the upsides to using a dc to dc charger. It will limit current to a precise amount. Sized properly, you're never in danger of overloading your alternator, plus it will properly charge your lifepo4 by precisely controlling the voltage applied to the battery. IMO $200-$300 for a dc to dc charger is a good insurance to protect both your motorhome and battery.
As for using a fuse as an alternator/battery current limiting device, that's not recommended. Fuses are very inexact devices. Some fuses can allow up to twice their current rating before they open. Fuses are primarily designed to protect in the event of a direct short.
What should I be looking for in a DC to DC charger given a 124A alternator and a 200AH lithium battery? I suppose it's possible I may add a second battery in the future as my motorhomes has space for two.
โNov-08-2021 05:51 AM
otrfun wrote:Teleman wrote:A BMS is not designed to function as a charger. It is designed as final line of defense to protect the battery.
I ordered a 200AH LifePo battery to replace my two 100AH lead acid batteries and also a compatabile converter which takes care of charging the battery with shore or generator power but what about charging the battery with the alternator? Does the battery's BMS take care of everything and therefore no need to change or upgrade the alternator? Sorry if this is a dumb question!
If you're counting on the wiring to/from the alternator to limit current between your alternator and batteries, you're going to have to choose the proper gauge wire or cable. Too big (physically), may allow excessive current (potentially overloading both the alternator and/or battery). Too little current will result in excessive charge times. There's no magical chart that's going to give you a precise answer. If you've priced copper wire lately, a trial and error approach could get very expensive. Also, if you change size/type of batteries in the future, you'll need to current match the wiring again.
That's one of the upsides to using a dc to dc charger. It will limit current to a precise amount. Sized properly, you're never in danger of overloading your alternator, plus it will properly charge your lifepo4 by precisely controlling the voltage applied to the battery. IMO $200-$300 for a dc to dc charger is a good insurance to protect both your motorhome and battery.
As for using a fuse as an alternator/battery current limiting device, that's not recommended. Fuses are very inexact devices. Some fuses can allow up to twice their current rating before they open. Fuses are primarily designed to protect in the event of a direct short.
โNov-08-2021 05:30 AM
otrfun wrote:
As for using a fuse as an alternator/battery current limiting device, that's not recommended. Fuses are very inexact devices. Some fuses can allow up to twice their current rating before they open. Fuses are primarily designed to protect in the event of a direct short.
โNov-08-2021 05:09 AM
Teleman wrote:A BMS is not designed to function as a charger. It is designed as final line of defense to protect the battery.
I ordered a 200AH LifePo battery to replace my two 100AH lead acid batteries and also a compatabile converter which takes care of charging the battery with shore or generator power but what about charging the battery with the alternator? Does the battery's BMS take care of everything and therefore no need to change or upgrade the alternator? Sorry if this is a dumb question!
โNov-07-2021 08:06 PM
โNov-07-2021 07:55 PM
Teleman wrote:time2roll wrote:
Dig in and find a part number.
Call Airstream.
Ask a workhorse chassis repair facility.
If you post the year, model etc someone might know.
OK thanks for your help.
โNov-07-2021 07:50 PM
time2roll wrote:
Dig in and find a part number.
Call Airstream.
Ask a workhorse chassis repair facility.
If you post the year, model etc someone might know.
โNov-07-2021 07:36 PM
โNov-07-2021 07:16 PM
time2roll wrote:Teleman wrote:Yes that video is a bit unrealistic so I recommend measuring your real situation.time2roll wrote:
OEM charging, boost start, bi-directional relay. Possible other options I don't know.
Yes the Victron shunt will tell you immediately if the amps are excessive. Excessive is primarily based on the wire and fuse rating.
Pardon my ignorance but what numbers would be excessive? I saw a YouTube video where the alternator overheated charging a lithium battery at a low rpm where it was passing a lot of current but not turning fast enough to cool itself with its internal fan
I read maybe 105 to 120 amp alternator is common with some old ones at 65 amp and some replacements at 200 amp. Depending on the battery size I would look for no more than 30% to 50% of alternator rating.
โNov-07-2021 07:12 PM
Teleman wrote:Yes that video is a bit unrealistic so I recommend measuring your real situation.time2roll wrote:
OEM charging, boost start, bi-directional relay. Possible other options I don't know.
Yes the Victron shunt will tell you immediately if the amps are excessive. Excessive is primarily based on the wire and fuse rating.
Pardon my ignorance but what numbers would be excessive? I saw a YouTube video where the alternator overheated charging a lithium battery at a low rpm where it was passing a lot of current but not turning fast enough to cool itself with its internal fan