(10-24-2022, 09:36 PM)kaptain Wrote: Quote:I would use a DC-DC charger between the chassis/house battery banks. That is, by far, the safest route.
The newer Renogy's are the best value for the money. You gain all of the benefits of the VSR (plus added intelligence), solar MPPT charger, reduced current, to lower the load on your alternator, and safer battery charge-rate (extending the life of the batteries). You also buy yourself a bit of future-proofing if you prefer to change battery chemistries in the future. All for only $100 (or so) more than a VSR or Isolator.
Could you please provide a product link to Renogy's new product that you mentioned, which is about $100 higher cost than the Blue Sea mentioned above?
I searched but didn't find any intelligent charger/separator rated over 100 amps.
I suspect I'm doing a bad job communicating because multiple objectives are being intermingled.
I'll try to take a step back, to correct any miscommunication:
Typically when you have multiple options within a market, those options are intended to serve different purposes. Or, in other words, there are pro's/con's to each approach.
I was attempting to explain that there are different products for different preferences, for example:
- If you want high-amperage charging at a low-cost, which protects against low/high-voltage, a good VSR with some intelligence (such as the BlueSea) is the best option.
- If you want to mix-chemistries or you want to limit the charging-current (despite your alternator being willing to produce a higher current), a DC-DC charger (such as the Renogy, Victron, Sterling) is the best option.
Unrelated to my points on technology, the theme of this post eventually turned to
protecting the alternator.
I believe there are only two practical methods to "protect" an alternator, either
(a) Use a special alternator-regulator to reduce the duty-cycle, either by
(i) intelligently reducing the run-time or current based upon temperature/SoC ...or...
(ii) Apply a simple, unintelligent run/cool-off cycle regardless of temperature or load -- or --
(b) reduce the current/amperage by limiting the demand.
Hardware options for the "alternator protection" objective:
- (a)(i) Regulate output (primarily based on temperature) with microcontroller setups (eg Wakespeed devices, Arduino devices, etc).
- (a)(ii) Cycle output (eg - 10 minutes on, 10 minutes off) statically, without intelligence.
- (a)* Important Note: cutting power-output can cause a power-dump that will ultimately fry the alternator's diodes; if going this route, add a protection device (eg Sterling).
- (b) Most common/beneficial: DC-DC Charger; regulating inrush, buck/boosting current where necessary, monitoring SoC, etc.
Ignoring the
(a) option; instead focusing on the
(b) option of DC-DC charger, the goal is using less current than the alternator produces. In most consumer-vehicles (I'm
not referring to DP's / semi's, etc) -- the alternator can only sustain about a quarter of its amperage-rating for long periods of time, without problems. It should go without saying that this is not a hard number but a very rough conservative average.
Therefore, in a consumer-vehicle, if you have a 200-amp alternator, you might prefer to limit your charging to 50-amps in the event you intend on long duty-cycles. In a diesel pusher, unlike a consumer-vehicle, perhaps you feel comfortable going higher.
You can choose the amperage that works best for you, based on your specific concerns/usage. If you prefer a higher amperage than is available in a single DC-DC charger, there are units that can be paralleled to increase charging amperage.
In short...
It would be impossible to have a conversation about how to leverage the maximum
rated-output of an alternator, while at the same time, how to reduce the potential impact on the alternator.
The two objectives are mutually exclusive.
If your concern is reducing load on the alternator or working with alternative battery chemistries/charge curves, or (depending on model) including voltage-sensitive cutoffs, the DC-DC chargers are a good option.
Alternatively, if you prefer to leverage 100% of our alternator's output and all of your batteries are SLA/AGM -- then you're better served with a VSR or similar.
I mentioned the Renogy DC-DC charger in the
sole context of being the safest option to protect alternators by reducing the current.
I don't believe that's your objective; if this is true, the DC-DC charger isn't ideal for you.
For others who need DC-DC chargers, there are a few Renogy options. I will include the Renogy options in response to your question; for those interest, there are also options available from Victron, Sterling, and many generic options.
In Renogy's case -- they have one product with an
MPPT solar charger built-in. That same product includes a VSR where it will enable the current flow when voltage is greater than 13.2 volts for 15 seconds. If voltage drops below 12.7 volts, it will cutoff. The user manual for that unit:
DCC50S DC-DC MPPT Manual (renogy.com) The only downside is that this unit is a lower amperage.
The alternative is a less robust charger that is purely DC-DC without features. It's available in 20, 40, 60 amp versions. This does not utilize as VSR; however, you can include protection by wiring to the ignition, where it will not allow a charge if the ignition circuit is open. The user manual for this group of units:
https://www.renogy.com/content/RNG-DCC12...Manual.pdf
I would like to reiterate that I'm not advocating this solution for your use. I have only intended to provide additional details to help answer your question, while at the same time, hoping to educate others who stumble upon this post in the future.
I hope some part of this can be helpful. Good luck to you
